This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A279425 #7 Oct 03 2023 18:47:36 %S A279425 16,112,150,163,166,169,172,186,211,218,227,242,244,246,248,250,252, %T A279425 254,256,258,273,282,289,314,1032,1037,1042,1056,1061,1075,1084,1089, %U A279425 1098,1107,1116,1125,1134,1138,1147,1160,1173,1177,1194,1198,1219,1223,1227 %N A279425 Numbers k such that k^2 has an odd number of digits and the middle digit is 5. %H A279425 Lars Blomberg, <a href="/A279425/b279425.txt">Table of n, a(n) for n = 1..10000</a> %e A279425 16^2 = 2(5)6, 218^2 = 47(5)24, 1075^2 = 115(5)625. %t A279425 Select[Range[1227], OddQ[len=Length[IntegerDigits[#^2]]]&&Part[IntegerDigits[#^2], (len+1)/2]==5 &] (* _Stefano Spezia_, Oct 03 2023 *) %Y A279425 Cf. A279420-A279424, A279426-A279429. %K A279425 nonn,base,easy %O A279425 1,1 %A A279425 _Lars Blomberg_, Dec 22 2016